Jeep UNIVERSAL CJ-2A - Accelerating Pump Circuit

'Jeep' UNIVERSAL and 'Jeep' DISPATCHER
F
through the idle adjusting screw seat just below.
This mixture is richer than the engine requires but
when mixed with the air coming past the throttle
valve a combustible mixture of the right propor-
tion for idle speeds is formed.
The idle port is slotted so that, as the throttle
valve is opened it will not only allow more air
to come in past it, but it will also uncover more of
the idle port allowing a greater quantity of fuel
and air mixture to enter the intake manifold.
When the idle speed position of the throttle is fixed
at 8 miles per hour [12,9 k.p.h.], it leaves enough
FIG. ll5-LOW-SPEED CIRCUIT
7-Idle Well Jet
8-Low Speed Jet
9-By-pass
1 0-Economizer
11-Lower Air Bleed
12-Idle Port
13-Idle Adjusting Screw
of the slotted port as reserve to cover the range in
speed between idle and the time when the high
speed system begins to cut in.
The idle adjusting screw varies the quantity of
the idle mixture.
F-5. High-Speed Circuit
The high-speed circuit, Fig. 116, cuts in as the throt-
tle is opened wide enough for a speed of about 20
miles per hour [32 k.p.h.]. The velocity of the air
flowing down through the carburetor throat creates
a pressure slightly less than atmospheric pressure
at the tip of the main nozzle. Since the fuel in
the float bowl is acted upon by atmospheric
pressure, the difference in pressure between the two
points causes fuel to flow from the bowl through
the metering jet and out the main nozzle int0 the
throat of the carburetor.
At higher speeds the area of the opening between
the metering ·jet and the metering rod governs
FIG. 116-HIGH-SPEED CIRCUIT
16-Metering Rod
17-Metering Jet 20-Main Nozzle
the amount of fuel entering the engine. At wide
open throttle only the smallest section of the rod
is in the jet.
F-6. Accelerating Pump Circuit
As the accelerator pedal is depressed, the pUmp
plunger and lever are forced downward. This forces
fuel
from the cylinder, closing intake ball check
valve, Fig. 117, and opening discharge ball check
valve passing the fuel into the throat of the
carburetor through pump jet.
10449
FIG. ll7-PUMP CIRCUIT
29-Intake Ball Check Valve
30-Discharge Ball Check Valve
33-Pump Jet
35-Pump Arm Spring
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